The long term goal of Project 2 is to develop safe and effective immunotherapy strategies for CNS tumors incorporating multi-disciplinary approaches that are being pursued in Projects 1 and 3. Despite the feasibility and safety of cancer vaccine-approaches, current evidence suggests that the systemic induction of anti-tumor immune responses by peripheral vaccines should be combined with modalities that enhance the homing and function of vaccine-induced effector cells within CNS tumor sites. Indeed, our studies from the prior funding period have indicated that genetic delivery of interferon (IFN)-alpha into CNS tumors facilitates the tumor-homing and therapeutic efficacy of Type-1 cytotoxic T-lymphocytes (CTLs) in an IFN-inducible protein (IP)-10 dependent manner. More relevant, underlying "prime-boost" regimen may be achieved in a more clinically feasible manner via administration of a "natural" inducer of IFN-alpha within the CNS-environment, such as a toll-like receptor (TLR)3 ligand, polyinosinic-polycytidylic acid (poly-IC), stabilized with poly-lysine and carboxymethylcellulose (poly-ICLC). Our preliminary studies with the GL261 glioma model have demonstrated that intramuscular (i.m.) administration of poly-ICLC improves the therapeutic effect of vaccinations with GL261-derived glioma-associated antigen (GAA) CTL epitopes by enhancing the homing of IFN-gamma expressing antigen-specific CTLs to the CNS tumor site. Based on the property of poly-ICLC to induce IFNs as well as IP-10, we hypothesize that administration of poly-ICLC effectively induces Type-1 GAA-specific effector cells as well as IP-10 at the tumor site, both of which are responsible for the enhanced efficacy of poly-ICLC-assisted vaccines. In Specific Aim (SA)1, we will determine whether promotion of Type-1 phenotype is the critical factor for the efficacy of poly-ICLC assisted GAA vaccines. Findings from these studies will allow us to determine the critical surrogate markers in our clinical trial proposed in SA3. In collaboration with Project 1 and 3, in our SA2, we will evaluate our hypothesis that inhibition of STATS signals may improve the efficacy of poly-ICLC assisted GAA-based vaccines. In addition, enhanced local IFN expression by tumor-infiltrating effector cells, may induce Indoleamine 2,3 dioxygenase (IDO), which inhibits proliferation of both T cells and Herpes-Simplex Viruses (HSV). We will determine whether poly-ICLC-assisted GAA-vaccines can be efficiently combined with HSV-therapy under the inhibition of IDO in collaboration with Project 3. We will implement a phase I/I I trial of vaccinations with human GAA-peptides identified during the initial funding period in conjunction with poly-ICLC in participants with recurrent malignant glioma. These proposed studies will provide a strong basis for a near future development of effective combination therapeutic strategies using vaccination with signal transduction modulation and/or HSV therapy.